Shoulder and other joint replacement techniques often require range of motion testing or other testing using a first, trial implant to initially evaluate a suitable position for the final implant. Generally, effective use of trial implants is dependent upon an ability to locate the final implant at substantially the same position and orientation as was used for the trial implant during evaluation. Often times, bone fractures or other damage impede use of boney landmarks or other bone features for implant positioning. For example, during shoulder replacement, proximal humerus fractures can impede a surgeon's ability to accurately position the final implant.
In typical humeral fractures, the proximal humerus breaks into two or three pieces, in what is called a three or four part fracture according to the Neer classification system. The broken pieces typically contain bony landmarks used to determine proper orientation and height for proper implantation of a humeral stem of a test and/or final implant. Therefore, a jig or other guide is needed to hold the trial implant during evaluation and then to hold the final implant. The final implant should generally replicate the same position of the trial implant, with a range of motion test being performed first on the trial implant and later the final implant. Generally, it is difficult to perform range of motion testing with jigs. Indeed, the jigs or guides are often moved, intentionally or inadvertently, in order to successfully perform range of motion testing, compromising replication of orientation and height from the trial implant to the final implant.